The present invention relates to new aqueous isocyanate emulsions containing an internal mold release agent and their use as binders in the production of shaped articles, in particular panels, preferably made of materials containing lignocellulose.
Pressed materials such as chip boards, composite panels and other shaped articles are usually produced by hot pressing an inorganic or organic raw material such as a composition of wood chips, wood fibers or other material containing lignocellulose with binders such as aqueous dispersions or solutions of urea/formaldehyde or phenol/formaldehyde resins. It is known to use isocyanate solutions as binders for pressed panels instead of urea/formaldehyde or phenol/formaldehyde resins (German Auslegeschrift No. 1,271,984; German Offenlegungsschrift No. 1,492,507 and German Offenlegungsschrift No. 1,653,177).
Processes for the production of panels or shaped articles are also known which involve pressing a mixture of lignocellulose material and an aqueous emulsion of an organic polyisocyanate (German Offenlegungsschriften Nos. 2,610,552; 2,703,271; 2,724,363 and 2,724,364).
Irrespective of their differing dispersibilities and reactivities toward water, known aqueous emulsions used as binders have the general disadvantage of causing separation problems at the interface between the shaped article and pressing tool so that the use of an external release agent is mandatory.
Objects of the present invention are to overcome these disadvantages and to provide new aqueous, self-releasing isocyanate emulsions.